Magento Open Source, 1.9.x
Modifying Categories

After a category is established, it can be edited, moved to another position in the category tree, or deleted from the catalog. However, if your catalog is live, you should consider how the change might impact any existing links to products in the category. For example, if your product URLs include the category path, and the category name is changed, any existing links to products in the category will be broken. To avoid this problem, you can configure your catalog to automatically create a permanent redirect if the URL key changes. You can also use the URL Rewrite tool to redirect traffic from an old URL to a new one.